Method for planarizing DRAM cells

Abstract

A method for planarizing DRAM cells comprising the steps of providing a silicon substrate having a field oxide layer, an oxide layer and a capacitor formed thereon, then forming a first dielectric layer over the substrate. Next, portions of the first dielectric layer is etched back to form a spacer layer, and then a second dielectric layer is formed over the spacer layer. Thereafter, an insulating layer is formed over the second dielectric layer. Finally, the insulating layer is fully etched back to form a third dielectric layer.

What is claimed is:  
     
       1. A method for planarizing semiconductor devices, comprising the steps of: 
       providing a silicon substrate having a surface topography;  
       forming a stacked layer free of conductive material, including:  
       forming a dielectric layer over the substrate, and etching back portions of the first dielectric layer to form a spacer layer;  
       forming a second dielectric layer having an upper surface and a lower surface opposite the upper surface, the lower surface being formed only directly on the conformal spacer layer; and  
       forming an insulating layer having an upper surface and a lower surface opposite the upper surface, the lower surface being formed only directly on the upper surface of the second dielectric layer; and  
       fully etching back the insulating layer, and etching back portions of the second dielectric layer to form a planar surface, with the insulating layer having an etching rate greater than the etching rate of the second dielectric layer.  
     
     
       2. The method of claim  1 , wherein the step of forming the first dielectric layer includes depositing borophosphosilicate glass. 
     
     
       3. The method of claim  1 , wherein the step of forming the first dielectric layer includes depositing tetra-ethyl-orthosilicate (TEOS). 
     
     
       4. The method of claim  1 , wherein the step of etching back the first dielectric layer includes using a dry etching method. 
     
     
       5. The method of claim  1 , wherein the step of forming the second dielectric layer includes depositing borophosphosilicate glass. 
     
     
       6. The method of claim  1 , wherein the step of forming the insulating layer includes spin coating spin on glass. 
     
     
       7. The method of claim  1 , wherein the step of forming the insulating layer includes depositing photo resist. 
     
     
       8. The method of claim  1 , wherein the step of fully etching back the insulating layer and etching back portions of the second dielectric layer includes the substeps of: 
       etching the insulating layer using a dry etching method;  
       simultaneously etching the insulating layer and the second dielectric layer when the second dielectric layer is partially exposed; and  
       continuously etching the insulating layer and the second dielectric layer until the whole insulating layer is etched away forming a third dielectric layer.  
     
     
       9. The method of claim  1 , wherein the step of fully etching back the insulating layer, and etching back portions of the second dielectric layer includes etching a borophosphosilcate glass layer. 
     
     
       10. A method for planarizing semiconductor devices, comprising the steps of: 
       providing a silicon substrate having a surface topography;  
       forming a stacked insulative layer free of conductive material, including:  
       forming a conformal first dielectric layer over the substrate's surface topography;  
       forming a second dielectric layer only over the conformal first dielectric layer; the second dielectric layer having an exposed nonplanar surface; and  
       forming an insulating layer only directly on the nonplanar surface of the second dielectric layer; and  
       fully etching back the insulating layer, and etching back portions of the second dielectric layer to form a planar surface, with the insulating layer, having an etching rate greater than the etching rate of the second dielectric layer.  
     
     
       11. The method of claim  10 , wherein the step of fully etching back the insulating layer and etching back portions of the second dielectric layer includes the substeps of: 
       etching the insulating layer using a dry etching method;  
       simultaneously etching the insulating layer and the second dielectric layer when the second dielectric layer is partially exposed; and  
       continuously etching the insulating layer and the second dielectric layer until the whole insulating layer is etched away, forming a third dielectric layer.  
     
     
       12. A method for planarizing semiconductor devices, comprising the steps of: 
       providing a silicon substrate having a surface topography;  
       forming a conformal first dielectric layer having a lower surface over the substrate's surface topography;  
       etching back portions of the first dielectric layer to form a conformal spacer layer;  
       forming a second dielectric layer having a nonplanar upper surface, such that the nonplanar upper surface and a lower surface opposite the upper surface, such that the nonplanar upper surface of the conformal spacer layer is contacted only by the second lower surface; and  
       forming an insulating layer having an upper surface and a lower surface opposite the upper surface, such that the nonplanar upper surface of the second dielectric layer is contacted only by the insulating layer lower surface, wherein the conformal spacer layer, the second dielectric layer and the insulating layer together form an insulating stacked layer that is conductor-free between the lower surface of the first dielectric layer and the upper surface of the insulating layer; and  
       fully etching back the insulating layer, and etching back portions of the second dielectric layer to form a planar surface, with the insulating layer having an etching rate greater than the etching rate of the second dielectric layer.